Chromium-molybdenum-carbon alloy



Patented Aug. 26, 1941 CHROMIUM-MOLYBDENUM-CARBON ALLOY Jacob Trantin,Jr., Youngstown, Ohio No Drawing.

Claims.

This invention relates to ferrous alloys capable of being cast, and,more particularly, is concerned with ferrous alloys having high wearresistance and freedom from scale pickup, and, specifically, adapted toform rolls, guides, and the like used to guide or form metal duringhandling or manufacture.

Prior to my present invention, plugs, guides and rolls of cast steel andof white or gray cast iron have been employed toguide, roll or otherwiseshape and handle steel or similar material during the process ofmanufacture. It is well understood that such cast iron or steel plugs,guides or rolls have a comparatively short life and are very subject toscratches, wear, and deposition of hot scale thereon. Plugs, guides orrolls which are scratched or marred, or have their surface covered witha layer of scale, often objectionably mar the work being guided orrolled. Eiiorts have been made to treat or harden the plugs, guides or'rolls, as by casting them against a chill, or by suitably heat treatingthe plugs, guides or rolls after casting. Nevertheless, because ofbrittleness, lack of wear-resistance, or susceptibility to scaledeposition, it has been recognized by those skilled in the art thatplugs, guides, rolls, or the like adapted to handle metal during itsmanufacture are subject to considerable improvement.

The heat treating of cast rolls, guides, plugs or other members adaptedto form or support metal or other material during the making thereof isa relatively expensive procedure and involves a very high degree ofskill. Also, one of the most serious objections to former practices hasbeen the outright failure of the guide, roll or plug in use which hasnecessitated a complete shutdown of the mill and the repair of thebroken part.

Not only have the means for supporting and forming hot or cold metalbeen unsatisfactory for the reasons set forth above, but also, many ofthe same difiiculties are encountered in handling, shaping, or guidingother materials during the transfer, shaping, handling or manufacturethereof. The same dliiiculties of lack of wear-resistance or'break downin use have been encountered.

It is the general object of my invention 'to avoid and overcome theforegoing andother difficulties of and objections to known means andmaterials by the provision of an improved alloy which may be directlycast into members for guiding, forming, conveying, transferring, orotherwise working orhandling materials or means,

Application June 18, 1941, Serial No. 398,566

and particularly hot and cold metal, and characterized by wearresistance, lack of susceptibility to metal deposit thereon,inexpensiveness to manufacture, and long life.

Another object of my invention is to provide an improved alloy which maybe directly cast to the desired shape, and which without treatmenteither during casting or afterwards will have a Brinell hardness of morethan 600, and which is characterized by extremely high wear resistance.

Another object of my invention is the provision ofan improved ferrousalloy characterized by very high stability against change in grainstructure and other physical characteristics under heat treatment, andinability to be materially affected by attempted annealing.

The foregoing and other objects of my invention are achieved by theprovision of an alloy having between about 1.5 and about 5.0 percentcarbon, between about 15.0 and 30.0 percent chromium, between about 1.5and about 10.0 percent molybdenum, up to about 10 percent copper, andthe remainder substantially all iron. The copper content, in general,serves to prevent hot metal deposition and where this is not animportant factor the copper may be omitted from the alloy whileretaining many of the advantages of the invention.

More particularly, I have discovered that certain distinctivecharacteristics in the improved alloy are achieved by holding the limitsof the alloying ingredients to substantially the following composition:Between about 2.5 and about 5.0 percent carbon; between about 20.0 andabout 30.0 percent chromium; between about 2.5 andabout 5.0 percentmolybdenum; up to about 5.0 percent copper; and the remaindersubstantially all iron.

One typical heat of the alloy of my invention which possesses thedesired characteristics of extreme hardness, long life, highwear-resistance. and. lack of susceptibility of scale depositioncomprises the following composition: Carbon about 3 percent; chromiumabout 25 percent; molybdenum about 3 percent; copper about 1.5 percent;and the remainder substantially all iron.

My improved alloy as manufactured in accordance with the last twoexamples given possesses certain striking and outstanding physicalcharacteristics. First, I have found that even when cast in an ordinarysand mold, and without any heat treating operations of any kind, that myimproved alloy has a Brinell hardness of over about600, and usually hasa Brinell hardless of over 700 and up to about 750 or even greater.Second, one of the most striking characteristics of my improved alloy isthat, so far as I have been able to determine, it shows little or noresponse to heat treatment. Efforts to anneal the alloy have resulted insubstantially no change in the hardness of the alloy, and I believe thatthis is due to the very stable characteristics of the chromium andmolybdenum carbides formed in the alloy.

If it is found desirable to provide an alloy retaining many of theadvantages already referred to, but, in addition, capable of beingannealed and heat treated, then the ingredients of my improved alloyshould be kept substantially within the following limits: Between about1.5 and about 2.5 percent carbon; between about 15.0 and about 20.0percent chromium; between about 1.5 and about 2.5 percent molybdenum; upto about 5.0 percent copper; and the remainder substantially all iron.

One typical heat of the alloy of my invention are important,nevertheless, my invention is particularly adapted to and concerned withthe provision of improved means for forming or guiding hot or cold metalduring rolling or shaping, and specifically, is concerned with providingrolls for skelp-forming mills or other mills for rolling bars, strips,and shapes of all kinds.

From the foregoing it will be recognized that I have achieved theobjects of my invention by providing a castable ferrous alloy which isinexpensive to manufacture, and possesses outstanding characteristics oflong life, wear resistance,

and freedom from scale pickup.

While in accordance with the patent statutes, I have particularlydescribed my invention, it

will be understood that I am not to be limited thereto or thereby, butthat the scope of my invention is defined in the appended claims.

I claim:

1. An alloy comprising between about 1.5 and about 5.0 percent carbon,between about 15.0 and about 30.0 percent chromium, between about 1.5and about 10.0 percent molybdenum, up to about 10 percent copper, andthe remainder substantially all iron, said alloy being characterized bya Brinell hardness of over 600 in its cast state and without heattreatment, and by particularly high wear-resistance.

2. An alloy comprising between about 2.5 and about 5.0 percent carbon,between about 20.0 and about 30.0 percent chromium, between about 2.5and about 5.0 percent molybdenum, up to about 5.0 percent copper, andthe remainder substantially iron, said alloy being characterized by aBrinell hardness of over about 700 and by extremely high wear resistancein the cast state, and by a stability of grain structure which rendersthe alloy substantially unaffected by annealing or heat treating.

3. An alloy comprising about 3 percent carbon, about 25 percentchromium, about 3 percent molybdenum, about 1.5 percent copper, and theremainder substantially all iron, said alloy being characterized byextremely high wear-resistance, and having a Brinell hardness of overabout 700 in the cast state.

4. An alloy comprising between about 1.5 and about 2.5 percent carbon,between about 15.0 and about 20.0 percent chromium, between about 1.5 a

JACOB TRANI'IN, JR. I

